Sound and Light

Honors Physics continued to explore sound with a discussion of sound intensity and loudness. Intensity is a function purely of the wave and distance from the source; loudness references how we perceive the intensity. We discussed the decibel scale and the effects of sounds in the “loud” range and beyond on humans. Attention then turned to the concept of resonance – a frequency-specific forced vibration in an object. We looked at some examples of resonance and will dig into this concept more deeply as we begin to study musical instruments. Tomorrow’s lab will allow you to work with basic concepts of sound, such as speed and features of the wave, and, if time permits, let’s you gain insight into how a touch-tone phone conveys information through tones.

Physical Science B investigated light in a series of three experiments. One experiment focused on reflectivity of light and few were surprised when dark colors and dull textures showed less reflectivity than lighter colors or shiny textures. The second experiment had students work with polarizing filters to document the transverse nature of light waves and to get an idea of how polarizing filters on cameras and polarizing sunglasses function to reduce glare. The final experiment targeted the inverse-square relationship associated with light intensity. As an observer moves away from a light source, the intensity drops quickly, as predicted by the formula: I = P/4πr². We’ll discuss these labs in class tomorrow and move on to examining reflection of light in more depth.

Physical Science E began discussing behaviors of light, starting with reflection. When light meets an impenetrable boundary, it is either absorbed by the material or reflected off of the material. While there is no material that is a perfect absorber or reflector, most things lean heavily in one direction. We contrasted specular and diffuse reflection, used the law of reflection to predicted reflected angles based on angles on incidence and started to examine reflection by plane mirrors. We’ll add curved mirrors to the list tomorrow, along with color.

Physics F and G embarked on their study of sound by revisiting basic properties of longitudinal and mechanical waves and then applying some sound-specific vocabulary to these concepts. Hearing and vocalization in various species was examined and the use of ultrasonic waves by humans and animals was described. Tomorrow, we continue on with sound, concentrating on loudness and resonance.

Homework\
Honors Physics A: Practice 13A #1-3, 13.2 Section Review
Physical Science B: Complete lab write up
Physical Science E: 15.3 Section Review
Physics F and G: Chapter 13 Review #21-23, 25, 26